A thermal processing chamber as used herein refers to a device that can heat a workpiece(s), such as a semiconductor wafer. The device can include a support plate for supporting the workpiece(s) and an energy source for heating the workpiece(s), such as heating lamps, lasers, or other heat sources. During heat treatment, the workpiece(s) can be heated under controlled conditions to a preset temperature regime. For instance, the workpiece(s) can be heated by an array of lamps through the support plate to temperatures of, for instance, from about 300° C. to about 1,200° C., for times that can be typically less than a few minutes in rapid thermal processing. During heat treatment, a primary goal can be to measure a workpiece temperature as precisely as possible.